In 1950s, computers were mainly used for scientific calculation and machine language programming, and graphic devices only had output function. Massachusetts Institute of Technology (MIT) uses cathode ray tube (CRT) as the graphic terminal on its Cyclone I computer, which can passively display graphics. Then the light pen appeared, and the research of interactive computer graphics began, paving the way for the emergence and development of CAD/CAM technology. 1952, MIT successfully trial-produced the CNC milling machine for the first time, and then developed the automatic programming language (APT) to realize computer-aided programming by describing the tool path, marking the beginning of CAM technology. 1956 is the first attempt to analyze aircraft structure with modern finite element method. At the end of 1950s, flat plotter and drum plotter appeared, which opened the history of computer drawing. Here CAD technology is in the brewing and preparation stage.
The 1960s was the most important period for the development of interactive computer graphics. 1963, that is, Sutherland, a scholar at Massachusetts Institute of Technology, published a doctoral thesis entitled "Graphical Communication System of Man-Machine Dialogue", and put forward terms such as computer graphics for the first time. His two-dimensional sketchpad system allows designers to operate the light pen and keyboard, perform interactive operations such as graphic selection and positioning on the graphic display, and use hierarchical data structure to store symbols and graphics. This research laid the foundation for interactive computer graphics and CAD technology, and also marked the birth of CAD technology. Since then, interactive graphic display, mouse, disk and other hardware devices, as well as file systems, high-level languages and other software have appeared. Many commercial CAD systems and equipment have appeared one after another. For example, in 1964, General Motors developed the DAC- 1 system for automobile design, Lockheed Aircraft Company developed the CADAM system in 1965, and Bell Telephone Company also introduced the GRAPHIC- 1 system. The application of CAD technology here is mainly two-dimensional drawing. In the manufacturing field, 1962 successfully developed the world's first robot, and realized the automation of material handling. 1965 CNC machine tool CNC system. After 1966, the DNC system which directly controls multiple CNC machine tools with a general computer and the automatic manufacturing system developed by Maureen company in Britain appeared. At the end of 1960s, Norway began to study CAPP technology, and in 1969, the first CAPP system, AutoPros, was officially launched.
In 1970s, the theory of computer graphics and computer drawing technology became more and more mature and widely used. During this period, the cost performance of hardware has been continuously improved; Graphics tablet and large-capacity disk storage appear correspondingly; Software such as database management system can be applied; The CAD/CAM system based on small and ultra-small computers has entered the market and become the mainstream. These systems are characterized by complete software and hardware, low price and convenient use, forming a so-called turnkey system. At the same time, three-dimensional geometric modeling software has been developed one after another, and some commercial CAD/CAM systems for small and medium-sized enterprises have appeared. Dassault France took the lead in developing CATIA, a three-dimensional surface modeling system featuring surface models. The research and development of CAPP system began in the mid-1970s. From 65438 to 0976, CAM-I Company developed the CAM-I automatic process planning system. In manufacturing industry, Cincinnati Company developed the Flexible Manufacturing System (FMS), which pushed CAD/CAM technology to a new stage. During this period, the functional modules of various computer-aided technologies have been basically formed, but the data structure is not uniform and the integration is poor. Applications mainly focus on 2D drawing, 3D wireframe modeling and finite element analysis.
In 1980s, CAD/CAM technology and its application system developed rapidly. During this period, microcomputers and 32-bit word-length workstations appeared. At the same time, the cost of computer hardware has been greatly reduced, and computer peripherals (color high-resolution graphic displays, large digitizers, automatic plotters, color printers, etc.). ) has gradually formed a series of products, network technology has also been applied. The combination of CAD and CAM forms the integrated technology of CAD/CAM, and a large number of new theories and algorithms are produced from it. In terms of software, not only the design calculation and drawing of engineering and products have been realized, but also engineering applications such as engineering modeling, free-form surface design, mechanism analysis and simulation have been realized, especially the development and application of solid modeling, feature modeling and parametric design, which has promoted the development of CAD technology from surface modeling to solid modeling to parametric modeling, and many mature CAD softwares have appeared. During this period, in order to meet the requirements of data exchange, relevant standards (such as CGI, GKS, IGES and STEP) have been issued one after another. In the late 1980s, people realized the importance of computer integrated manufacturing (CIM) and began to emphasize information integration. The appearance of CIMS has pushed CAD/CAM technology to a new height.
Since 1990s, CAD/CAM/CAE technology has put more emphasis on information integration and resource sharing, and product data management technology has emerged, and CAD modeling technology has become more and more perfect, and many mature commercial softwares of CAD/CAE/CAM integration have emerged, such as I-DEAS with variable technology and UG with composite modeling technology. With the changeable and fierce competition in the world market, with the development of various advanced design theories and advanced manufacturing modes, with the development of high-grade microcomputers, operating systems and programming software, and with the rapid development of network technology, CAD/CAM/CAE technology is experiencing unprecedented development opportunities and challenges, and is developing towards integration, networking, intelligence and standardization. A perfect CAD/CAM/CAE system should have the following functions: fast digital calculation and graphics processing, geometric modeling, NC machining information processing, storage and rapid retrieval and operation of a large number of data and knowledge, man-machine interaction, input and output information and graphics, engineering analysis, etc. In order to realize these functions, the running environment of CAD/CAM/CAE system consists of hardware, software and people.
Hardware mainly includes tangible equipment such as computers and their peripherals. Generalized hardware also includes mechanical equipment and machine tools for NC machining. Hardware is the foundation of CAD/CAM/CAE system, and every technical breakthrough of hardware brings revolutionary changes in CAD/CAM/CAE technology. Software is the core of CAD/CAM/CAE system, including system software, various supporting software and application software. Hardware provides the potential ability of CAD/CAM/CAE system, and the realization of system functions is completed by software running in the system. With the continuous improvement and improvement of the functions of CAD/CAM/CAE system, the proportion of software cost in the whole system is increasing. At present, the price of some high-end software is much higher than that of system hardware.
Any powerful computer software and hardware are only auxiliary design tools, and how to give full play to the functions of the system mainly depends on the quality of users. The operation of CAD/CAM/CAE system is inseparable from people's creative thinking activities, and the key role of people in the system is self-evident. 265438+At the beginning of the 20th century, CAD/CAM/CAE system basically adopted the mode of human-computer interaction, which required people to cooperate closely with computers to give full play to their respective strengths: computers have unique functions in information storage and retrieval, analysis and calculation, graphics and word processing. People play a leading role in creative thinking, comprehensive analysis and empirical judgment. The hardware of CAD/CAM system is mainly composed of computer host, external memory, input equipment, output equipment, network equipment and automatic production equipment. There are special input and output devices to deal with the interactive input and output of graphics, which is the obvious difference between CAD/CAM/CAE system and general computer system.
(1) computer host
Host is the hardware core of CAD/CAM/CAE system, which is mainly composed of central processing unit (CPU) and memory (also called memory). The CPU includes a controller and an arithmetic unit. The controller directs and coordinates the work of the whole computer according to the instructions taken from the memory, and the arithmetic unit is responsible for executing the numerical calculation and logical operation required by the program instructions. The performance of CPU determines the data processing ability, operation accuracy and speed of computer. Memory is a storage unit that CPU can directly access to store resident control programs, user instructions, data and running results. There are two main indicators to measure host performance: CPU performance and memory capacity. According to the different performance levels of the mainframe, computers can be divided into large and medium-sized computers, small computers, workstations and microcomputers.
(2) External memory
External memory, referred to as external memory, is used to store programs, data and other information that are temporarily unused or waiting to be called. When this information is used, the operating system will call it into memory according to the command. External memory is characterized by large capacity, often reaching hundreds of MB, dozens of GB or even more, but the access speed is slow. Common ones are magnetic tape, magnetic disk (floppy disk, hard disk) and optical disk. With the development of storage technology, mobile storage devices such as mobile hard disk and U disk have become an important part of external storage.
(3) Input devices
Input equipment refers to the equipment that converts various external data into electronic pulse signals that can be recognized by the computer through human-computer interaction. It is mainly divided into keyboard input (such as keyboard), pointing input (such as mouse), graphic input (such as digitizer), image input (such as scanner and digital camera) and voice input.
(4) Output equipment
A device that converts data processed by a computer into the form required by users is called an output device. Output devices can display the intermediate or final results and processes of computer operations in the form of words, graphics, images and sounds, so as to realize direct communication with the outside world. Common output devices include display output (such as graphic display), print output (such as printer), drawing output (such as automatic plotter), image output and voice output.
(5) Network interconnection equipment
Including network adapters (also known as network cards), repeaters, hubs, bridges, routers, gateways, modems and other devices, connected to the network through transmission media to achieve resource sharing. The connection mode of the network, namely the topological structure, can be divided into star structure, ring structure, tree structure, mesh structure and other structures. Advanced CAD/CAM systems all appear in the form of network. In order to give full play to the role of computer hardware, CAD/CAM/CAE system must be equipped with fully functional software, and the grade and level of software configuration is the key factor to determine the function, work efficiency and ease of use of the system. Computer software refers to computer programs, data and various related documents that control the operation of CAD/CAM/CAE system and make the computer play its greatest role. A program is a collection of instructions for processing data and directing the work of computer hardware, and it is the main content of software. Documents refer to the results of program processing, databases, instructions, etc. Documentation is the basis of program design, and its design and compilation level largely determines the quality of software. Only with qualified and complete documents can the software be commercialized.
According to the different tasks and processing objects, the software of CAD/CAM/CAE system can be divided into three different levels: system software, supporting software and application software. System software is directly related to computer hardware, which plays the role of expanding computer functions and reasonably scheduling and using computer hardware resources. The supporting software runs on the system software and is the tool and foundation of various application software, including general application basic software for realizing various functions of CAD/CAM/CAE. Application software is a special software to realize a specific task in an application field with the support of system software and supporting software.
(1) system software
System software is the link between users and computer hardware, and it is a collection of running programs that use, control and manage computers. System software is usually developed by computer manufacturers or software companies. The system software has two remarkable characteristics: first, it is universal, and users in different application fields need to use the system software; The second is basic, that is, both supporting software and application software need to run with the support of system software. Firstly, the system software provides a clear, concise and easy-to-use friendly interface for users to use computers. The second is to make full and reasonable use of various resources in the computer system as much as possible. The system software mainly includes three parts: operating system, programming language system and network communication and management software.
Operating system is the core of system software and the soul of CAD/CAM/CAE system. It controls and directs the software resources and hardware resources of the computer. Its main functions include hardware resource management, task queue management, hardware driver, timing and time-sharing system, basic mathematical calculation, daily affairs management, error diagnosis and correction, user interface management and job management. The operating system depends on the hardware of the computer system. Users use the computer through the operating system, and any program can only be executed after the operating system allocates the necessary resources. The popular operating systems in the 20th century include Windows, UNIX and Linux.
Programming language system mainly completes source program editing, library function and management, grammar checking, code compilation, program connection and execution. According to different programming methods, it can be divided into structured programming language and object-oriented programming language; According to the degree of dependence on computer hardware when programming, it can be divided into low-level language and high-level language. Object-oriented programming languages, such as Visual C++, Visual Basic and Java, were widely used in the 20th century.
Network communication and its management software mainly include network protocol, network resource management, network task management, network security management, communication browsing tools, etc. The international standard network protocol is open system interconnection, which is divided into seven layers: application layer, presentation layer, session layer, transport layer, network layer, data link layer and physical layer. The main popular network protocols in CAD/CAM/CAE system are TCP/IP protocol, MAP protocol, TOP protocol and so on.
(2) Supporting software
Supporting software is an important part of CAD/CAM software system, which is generally developed by commercial software companies. The supporting software is a general CAD/CAM/CAE software that meets the needs of * * *, and it is a knowledge-intensive product. This kind of software is not aimed at specific application objects, but provides tools or development environment for users in a certain application field. Supporting software generally has good data exchange performance, software integration performance and secondary development performance. According to the function of supporting software, it can be divided into single-function software and integrated software. Single function support software only provides functions of some typical processes in CAD/CAM/CAE system, such as interactive drawing software, three-dimensional geometric modeling software, engineering calculation and analysis software, numerical control programming software, database management system and so on. Functional integration support software provides comprehensive functional modules such as design, analysis, modeling, numerical control programming and machining control.
1) interactive drawing software
This kind of software mainly completes the generation and drawing of two-dimensional engineering drawings in an interactive way, and has the functions of editing, conversion, storage, display control, dimensioning and so on. With the function of parametric drawing driven by size; There is a relatively complete parametric library of mechanical standard parts. This kind of software has strong drawing function, convenient operation and low price. Typical products used by microcomputers are AutoCAD, CAXA electronic drawing board, PICAD, Gaohua CAD, etc.
2) 3D geometric modeling software
This kind of software mainly solves the structural design problems of parts and provides users with complete and accurate methods and tools to describe and display three-dimensional geometric shapes. It has the functions of blanking, coloring, coloring, solid parameter calculation, quality characteristic calculation, parametric feature modeling, assembly, interference inspection and so on, and has the functions of simple surface modeling, moderate price, easy learning and mastering. The applications of this kind of software in China are mainly MDT, SolidWorks and SolidEdge.
3) Engineering calculation and analysis software
The functions of this kind of software mainly include basic physical quantity calculation, basic mechanical parameter calculation, product assembly, tolerance analysis, finite element analysis, optimization algorithm, mechanism kinematics analysis, dynamics analysis, simulation and so on. Finite element analysis is the core tool. Adams.
4) CNC programming software
This kind of software generally has the functions of tool definition, process parameter setting, automatic tool path generation, post-processing and cutting simulation. MasterCAM, SurfCAM and CAXA manufacturing engineers are widely used.
5) Database management system
Engineering database is an important part of CAD/CAM/CAE integrated system. Engineering database management system can effectively store, manage and use engineering data, and support data transmission and sharing among subsystems. The development of engineering database management system can be modified or supplemented according to the engineering characteristics on the basis of general database management system. The popular database management systems in 2 1 century include ORACLE, SYBASE, FOXPRO, FOXBASE, etc.
(3) Functional integration software
1) major/engineer
2)UG
3)DEAS Island
4)CATIA